Referring to FIG. 1, a gas turbine engine is generally indicated at 10 and comprises, in axial flow series, an air intake 11, a propulsive fan 12, an intermediate pressure compressor 13, a high pressure compressor 14, a combustor 15, a turbine arrangement comprising a high pressure turbine 16, an intermediate pressure turbine 17 and a low pressure turbine 18, and an exhaust nozzle 19.
The gas turbine engine 10 operates in a conventional manner so that air entering the intake 11 is accelerated by the fan 12 which produce two air flows: a first air flow into the intermediate pressure compressor 13 and a second air flow which provides propulsive thrust. The intermediate pressure compressor compresses the air flow directed into it before delivering that air to the high pressure compressor 14 where further compression takes place.
The compressed air exhausted from the high pressure compressor 14 is directed into the combustor 15 where it is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive, the high, intermediate and low pressure turbines 16, 17 and 18 before being exhausted through the nozzle 19 to provide additional propulsive thrust. The high, intermediate and low pressure turbines 16, 17 and 18 respectively drive the high and intermediate pressure compressors 14 and 13 and the fan 12 by suitable interconnecting shafts.
In view of the above it will be appreciated that certain parts of the engine 10 and in particular the low pressure compressor stages of that engine may be subject to icing on components such as guide vanes. In appropriate atmospheric conditions, icing of components may occur at any time when the engine is running, that is to say in use. This includes ground running, at idle or at higher engine speeds, as well as operation in flight. In such circumstances ice may build up on these guide vanes, which will then eventually be shed potentially causing damage to subsequent parts and stages of the engine 10. In order to avoid such ice build-up it has been known for hollowing of these components to be provided in order that hot air from the combustor or other stages of the engine can then be used to warm the component and therefore prevent ice build-up. Unfortunately hollow components increase engine complexity and therefore production costs and so result in extended manufacturing timescales. Furthermore, components which move or rotate add additional complexity and potential leakage through the need to provide hot air flow through a rotating spindle to the component for heating to avoid icing on that component.